1. Field of the Invention
The present invention relates to a preferred digital broadcast receiving tuner for use with a television set with a VCR or the like.
2. Description of the Prior Art
In a conventional digital broadcast receiving tuner, for example, a digital broadcast receiving tuner for use with a television set with a VCR, two tuners of a tuner for television and a tuner for a VCR are individually prepared respectively, and these two tuners are attached to a mother board respectively.
Thus, telecasting is adapted to be received by a tuner for a television, while the telecasting is picture-recorded by a tuner for a VCR, and the tuner for a VCR is adapted to, while receiving television by the tuner for a television, be able to picture record broadcast through the same channel or another channel.
The conventional digital broadcast receiving tuner cannot be miniaturized partly because two tuners are individually manufactured, which causes low productivity and high cost, and partly because those two tuners are installed side by side on one surface of a mother board, which increases the size of the mother board area that is used for mounting the tuners.
Thus it is an object of the present invention to provide a low-priced digital broadcast receiving tuner suitable for miniaturization.
As a first solution to the above-described problem, a structure is arranged such that the digital broadcast receiving tuner has an insulating board provided with a wiring pattern each on both surfaces thereof, and that on one surface of this insulating board there is formed a first tuner while on the other surface thereof there is formed a second tuner.
Also, as a second solution, the insulating board is structured of a stacked multi-layer board, and the structure is arranged such that the first and second tuners are electrically shielded from each other by a grounding conductor layer provided within the multi-layer board.
Also, as a third solution, a structure is arranged such that the first and second tuners have a high-frequency unit and a demodulation unit respectively, and that the high-frequency unit of the first tuner and the demodulation unit of the second tuner, and the demodulation unit of the first tuner and the high-frequency unit of the second tuner are arranged at a position opposite to each other with the multi-layer board interposed therebetween respectively.
Also, as a fourth solution, a structure is arranged such that the multi-layer board is formed of at least three layers; between the lamination layers, there are provided at least the two grounding conductor layers; in a region in which the high-frequency unit is provided, the grounding conductor layers arranged near the high-frequency unit are provided with a deletion unit; and in a range in which the demodulation unit is provided, the grounding conductor layers arranged near the demodulation unit are provided with a first remainder to thereby increase a facing distance between the wiring pattern of the high-frequency unit and the first remainder.
Also, as a fifth solution, a structure is arranged such that the high-frequency unit has an IC component having a direct conversion unit including an oscillator and a mixer, and that the grounding conductor layer arranged near the high-frequency unit is provided with a second remainder to oppose a lower portion of the IC component.